(1) Field of the Invention
The present invention relates to a method of producing water-in-oil emulsion explosive (hereinafter, referred to as W/O emulsion explosive), and more particularly relates to a method of producing W/O emulsion explosive commercially advantageously, wherein relatively unstable hollow microspheres can be stably kneaded with W/O emulsion in a short time through a kneading step, wherein agitating blades fitted to an agitating shaft in a kneader are moved in the axial directions of the agitating shaft and are concurrently rotated to improve the kneading efficiency, and the kneaded mixture is exhausted from the kneader by means of extruding blades fitted to the lower portion of the agitating shaft.
(2) Description of the Prior Art
It is generally important to produce safely W/O emulsion explosion in a commercial scale and to control the quality of the resulting explosive regardless of continuous process and batch process.
U.S. Pat. No. 4,138,281 specification discloses a method of producing W/O emulsion explosive comprising aqueous solution of inorganic oxidizer, oil, emulsifier and hollow microspheres. This method comprises five steps as illustrated in FIG. 1, that is, a step for conditioning an aqueous solution of inorganic oxidizer, a step for conditioning a mixture of oil and emulsifier, a step for emulsifying the mixture of oil and emulsifier together with the above described aqueous solution of inorganic oxidizer into a W/O emulsion, a step for kneading the resulting W/O emulsion together with hollow microspheres, and a step for packing the resulting W/O emulsion explosive. Among these steps, the emulsifying and kneading steps are most important. It is necessary to produce a strong W/O emulsion in the emulsifying step, and whether the resulting W/O emulsion has been fully emulsified or not has a high influence upon the quality and storage stability of the W/O emulsion explosive produced from the emulsion. Particularly, when the formation of emulsion is insufficient, the resulting W/O emulsion explosive deteriorates in its detonation sensitivity at low temperatures and in its explosion performance during its storage for a long period of time. The kneading step is carried out in order to knead homogenously a W/O emulsion having a relatively large specific gravity with hollow microspheres having a very small specific gravity. In this case, the hollow microspheres are easily broken by mechanical shear due to their inherent property and therefore it is an important problem how to knead the hollow microspheres with a W/O emulsion within a short time without causing breakage. Even when a W/O emulsion and hollow microspheres can be homogeneously kneaded, if the hollow microspheres are broken during the kneading, the resulting explosive is poor in the quality and is very poor in the explosion performance.
The inventors have variously attempted for a long period of time in order to solve the above described problems and to develop a new technic, and have newly found out a very excellent kneading method. Further, the inventors have ascertained that a W/O emulsion explosive produced by the newly found out method is less in breakage of hollow microspheres, and is more excellent in homogeneity than W/O emulsion explosives produced by a conventional method, and further ascertained that the W/O emulsion explosive of the present invention is superior or equal to the conventional W/O emulsion explosives in explosion performance and other properties. As the result, the present invention has been accomplished.